German Auslegeschrift No. 12 21 893 discloses the manufacture of coated printing papers, wherein starch is made partially cold-soluble by mechanical treatment in a pug mill, so that in the drying operation performed after the coating it will still be dissolved by the evaporating moisture of the coating composition and as a binding agent will contribute in conventional manner to the fixation of the pigments such as chalk. The manufactured papers are confirmed as having a high gloss. The problem of the resistance of the printing inks to scrubbing is not addressed.
Canadian Patent 1,043,193 (German Patent No. 26 05 575) discloses a bank note paper in which, for the avoidance of fiber separation and for improving resistance to soiling, the surface is provided with a coating which contains as a special plastic binder 0.5 to 10 parts by weight of very fine rice starch, and in some cases additional inorganic pigments. The problem of scrub-resistance does not occur in such papers.
The outstanding suitability of matte, non-glossy printing papers for high-quality printwork, such as art books, advertising folders and business reports, has been increasingly recognized in recent years. Matte printing papers have the great advantage that, on the one hand, the printed products produced with them do not create disturbing light reflections when viewed, and on the other hand, in conjunction with appropriate printing inks, the actual print, especially the polychrome print, has a quite outstanding print gloss, thereby enhancing the quality of the printed product.
For the production of such matte-coated printing papers, the use of calcium carbonate has advanced on a broad front in recent years.
In the German publication, "Wochenblatt far Papier-fabrikation," Vol. 112, No. 17, pages 609 to 613 (1984), the properties of matte-coated papers, including those having calcium carbonate as a coating component, are extensively discussed. In spite of their widespread use since the middle 70's, a great deficiency in regard to scrub-resistance and the formation of glossy streaks is cited as a decided disadvantage of these papers.
Scrub-resistance is to be understood to mean the resistance of a layer of printing ink to mechanical stress by pressure and friction in the further processing of the printed sheet and in the use of the finished printed product.
Even in the case of unprinted papers, however, scrubbing can lead to undesired gloss effects in the finishing machines of the paper mill, such as crosscutters, for example, so that the usefulness of a matte-coated paper can thus be reduced to zero.
Various measures are proposed in the above-cited literature to improve scrub-resistance, but all are relatively difficult to realize or they make the end product expensive, for example if the finished printing sheet is coated with an additional matte lacquer finish. The proposed measures still have not led to a satisfactory solution.